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SO017/#193  Identification of P53 subclone improves immunohistochemistry and NGS agreement in endometrial carcinoma and predicts good prognosis
  1. Yan Xu1,
  2. Yangyang Jiang1,
  3. Yanjiao Hu2,
  4. Han Zhao2,
  5. Jinwen Jiao1 and
  6. Qin Yao1
  1. 1The Affiliated Hospital of Qingdao University, Department of Obstetrics and Gynecology, Qingdao, China
  2. 2The Affiliated Hospital of Qingdao University, Department of Pathology, Qingdao, China


Introduction Using the p53 immunohistochemical staining pattern (IHC) as a marker of TP53 gene mutation, IHC and next-generation sequencing (NGS) have a high agreement in ovarian cancer, but the agreement in endometrial cancer (EC) remains to be improved. In addition to overexpression, non-expression, and cytoplasmic expression, there is also subclonal abnormal expression pattern of p53 immunohistochemical abnormality in endometrial cancer. However, there are few studies on subclonal expression in endometrial cancer.

Methods A total of 1869 patients who underwent surgical treatment for ECs between January 2019 and November 2022 were included in the study. Of these, 167 patients with both p53 immunohistochemistry and TP53 NGS results were further analyzed.

Results Abnormal p53 subclonal staining was observed in 14 cases (8.4%) of ECs, and the agreement increased from 80.2% to 93.4% after the identification of subclonal types. IHC and NGS detected disagreement in 11 cases, all of which were missense mutations in the DBD (DNA binding domain). Among the 14 subclonal cases, 9 cases were POLEmut-p53abn or MMRd-p53abn multimolecular typing, and 5 cases were p53abn. Excluding the POLEmut/MMRd agreement reached 95.0%. The subclones had better prognosis compared with other p53 abnormal patterns and wild type (p<0.05).

Abstract SO017/#193 Figure 1

Clinical, molecular, histopathological characteristics and TP53 mutations frequency and domain site of 167 EC patients. A. Clinical, molecular, and histopathological characteristics of 167 EC patients, some patients have detected more than one mutation, so the table will show multiple colors. B. In this study and TCGA UCEC datasets, each identified TP53 mutation is shown as a lollipop plot along the protein domain, showing positions and counts. C,D. Matching and mismatching situations between p53 IHC staining and NGS mutation in each domain

Abstract SO017/#193 Figure 2

p53 IHC subclonal expression predicts good prognosis in endometrial carcinoma. A. A mixed case (high grade serous and EEC), though the gene tests as missense mutations in the DBD domain (V216M, R175H), but the p53 stain shows a combination of diverse p53 staining patterns and clear boundaries can be observed, which is a subclonal type classified as MMRd-p53abn. P53 IHC changed from WT to subclonal abnormal expression, which is consistent with the results of gene sequencing. *EEC, endometrioid endometrial cancer, DBD domain, DNA-binding domain. B. A case of EEC1–2 without POLEmut or MMRd, is detected of missense mutation (H193L) in the DBD domain and classified as p53abn. It has two different p53 patterns in the same slice, which is convinced as subclonal expression, instead of initially diagnosed with WT(focal overexpression), it is considered agreement. C. Prognostic relevance of p53 IHC and molecular classifier. (A). p53 subclone with other p53 abnormal patterns (overexpression, null, cytoplamsic) and wild type. (B). Comparison of TP53 mutation types. (C) Single-classifier of EC according to WHO standards. (D). Comparison of Multi-classifier (POLEmut-p53abn and MMRd-p53abn) and Single-classifier

Conclusion/Implications Recognize the p53 subclonal staining pattern in EC is the main reason affecting agreement. Accurately identifying abnormal subclonal expression can improve the agreement of p53 IHC and TP53 NGS in endometrial cancer. The p53 IHC subclone is associated with POLEmut-p53abn or MMRd-p53abn multi-molecular typing and may have a good prognosis.

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